Transcript presentation for RACE Aveiro - Robotics and Automation Careers in

Robotics and Automation Careers in Engineering (R.A.C.E project)
• Components of a servomotor are:
- a DC electric motor,
- gears with an output shaft;
- position-sensing mechanism;
- control circuitry.
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Motor wiring and plugs
A great advantage of servomotors is that they are very easy to
control in comparison with other types of motors (DC, Stepper) that
require an H-Bridge or external circuitry. The servo motor has all this
circuitry internally.
The differences of a servomotors in according to elements from its
construction are:
- the colours of wires;
- the type of spline used.
- the type of connector used;
The Servo Motors comes with three wires (leads). Two of these wires
are to provide ground and positive supply to the servo’ s DC motor. The
third wire is for the control signal.
Robotics and Automation Careers in Engineering (R.A.C.E project)
Wires’ signification for a different brands of
servomotors are:
Unlike DC motors, reversing the ground and positive supply
connections does not change the direction (of rotation) of a servo.
This may, in fact, damage the servo motor.
Robotics and Automation Careers in Engineering (R.A.C.E project)
The type of splines for a servomotors are:
Spline is the place where a servo arm (horn) is connected. It is analogous to the
shaft of a common DC motor.
- Hitec splines has 24 teeth;
- Futaba splines has 25 teeth.
The splines made for one servo type cannot be used with another.
Robotics and Automation Careers in Engineering (R.A.C.E project)
The type of plugs for a servomotors are:
- Futaba provides a J-type plug with an extra flange for proper
connection of the servo.
- Hitec has an S-type connector.
Futaba connector can be used with a Hitec servo by clipping
of the extra flange. Also a Hitec connector can be used with a
Futaba servo just by filing off the extra width so that it fits in well.
Robotics and Automation Careers in Engineering (R.A.C.E project)
Inside a Servomotor
.
Robotics and Automation Careers in Engineering (R.A.C.E project)
Inside a Servo Motor
.
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control
- The servo motor can be moved to a desired angular position by
sending PWM (pulse width modulated) signals on the control wire.
- A pulse of width varying from 1 millisecond to 2 milliseconds in a
repeated time frame is sent to the servo for around 50 times in a
second. The width of the pulse determines the angular position. When
the servo receives a pulse, it can retain the corresponding angular
position for next 20 milliseconds. So a pulse in every 20 millisecond time
frame must be fed to the servo.
- For continuous servo, a pulse of 1 ms moves the servo towards 0°,
while a 2 ms wide pulse would take it to 180°;
- For standard servo, a pulse of 2 ms moves the servo towards 0°,
while a 1 ms wide pulse would take it to 180°;
- The pulse width for in between angular positions can be interpolated
accordingly. Thus a pulse of width 1.5 milliseconds will shift the servo to
90°.
- It must be noted that these values are only the approximations. The
actual behavior of the servos differs based on their manufacturer.
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control for standard servo
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control for standard servo
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control for standard servo
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control for standard servo
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control for standard servo,using PBasic
programming language
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control for continuous servo
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control for continuous servo
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control for continuous servo
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control for continuous servo
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo Control for standard servo,using PBasic
programming language
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo control without programming (using
a 555 timer circuit)
Robotics and Automation Careers in Engineering (R.A.C.E project)
Servo control without programming (using
a 555 timer circuit)
Total
Qty.
Part
Description
R1
1
820 Ohm 1/4W Resistor
R2
1
68K 1/4W Resistor
R3
1
10K 1/4W Resistor
R4
1
1K 1/4W Resistor
R5
1
1K Linear Taper Pot
C1
1
1uF 16V Electrolytic Capacitor
Q1
1
2N3904 NPN Transistor
U1
1
555 Timer IC